Transmitter, RF transmitter signal processor and method for operation of transmitter

ABSTRACT

An internal operation of RF IC is adjusted so that the level of an RF transmitter signal is substantially stopped from rising, or made to descend in course of ramp-up of the RF transmitter signal. This adjustment is enabled by ramp-up adjustment data Last 4 symbols contained in preamble data precedent to real transmission data transmitted after completion of ramp-up. The ramp-up adjustment data and real transmission data are supplied from a baseband LSI. The RF transmitter signal contains phase and amplitude modulation components according to the EDGE system. RF IC includes phase and amplitude modulation control loops PM LP and AM LP. Ramp-up of RF power amplifiers PA 1  and PA 2  is performed by controlling the gain of the first variable amplifier MVGA included in the AM LP according to ramp information. Thus, unwanted radiation&#39;s level is reduced during ramp-up of the RF transmitter signal of the RF power amplifiers.

CLAIM OF PRIORITY

The Present application claims priority from Japanese application JP2007-118199 filed on Apr. 27, 2007, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a transmitter, an RF transmittersignal-processing circuit used therefor, and a method for operating thetransmitter. Particularly, it relates to a technique beneficial toreduce the level of unwanted radiation in ramp-up and ramp-down of an RFtransmitter signal of an RF power amplifier.

BACKGROUND OF THE INVENTION

As to communications terminal devices such as mobile phone terminals,there has been known TDMA system, in which time slots can be set for anidle state, an operation to receive a signal from a base station or anoperation to send a signal to the base station. Incidentally, TDMA is anabbreviation of Time-Division Multiple Access. As the TDMA systems havebeen known GSM system and GMSK system, which use only phase modulation,provided that GSM is an abbreviation of Global System for MobileCommunication, and GMSK is an abbreviation of Gaussian minimum ShiftKeying. In contrast with GSM and GMSK systems, systems which improve acommunication data transfer rate have been known. As one of suchimprovement systems, EDGE system using amplitude modulation in parallelwith phase modulation has been attracting attention recently.Incidentally, EDGE is an abbreviation of Enhanced Data for GSM Evolutionor Enhanced Data for GPRS, and GPRS is an abbreviation of General PacketRadio Service.

As a method to materialize the EDGE system has been known a polar loopsystem including: separating a transmitter signal, which must be sentout, into phase and amplitude components; then performing respectivefeedback controls with phase and amplitude control loops; and combiningphase and amplitude components gained after the feedback controls bymeans of an amplifier.

A polar loop transmitter having a phase control loop and an amplitudecontrol loop and supporting an EDGE transmitter function is described inthe Non-patent Document presented by Earl McCune, “High-Efficiency,Multi-Mode, Multi-Band Terminal Power Amplifiers”, IEEE microwavemagazine, March 2005, PP. 44-45. According to the document, it isdescribed that the power efficiency is a key market issue for mobilephones, and in a polar loop system, an RF power amplifier operating in acondition near saturation offers the advantage of a better powerefficiency. Also, it is described that an additional advantage of thepolar loop system posed by an operation of an RF power amplifier in suchnear-saturation condition is low-noise characteristics.

In contrast, specifications of a digital interface between an RF IC anda baseband LSI are stated in the Non-patent Document presented by AndrewFogg, “DigRF BASEBAND/RF DIGITAL INTERFACE SPECIFICATION”, Logical,Electrorical and Timing Characteristics EGPRS Version Digital InterfaceWorking Group Rapporteur Andrew Fogg, TTPCom Version 1.12http://146.101.169.51/DigRF Standard v112.pdf (according to search onOct. 5, 2006).

SUMMARY OF THE INVENTION

Prior to the present invention, the inventors had been engaged indevelopment of an RF communication semiconductor integrated circuit,hereinafter referred to as “RF IC”, which has a transmitter including adigital interface with a baseband LSI and enables transmission in multimodes of GMSK and EDGE systems.

It is required for EDGE amplitude modulation to control an RFtransmitter signal in amplitude. Control information for EDGE amplitudemodulation is contained in a transmission baseband signal produced by abaseband LSI. The control information for EDGE amplitude modulationdetermines the amplitude of an RF transmitter signal produced by an RFIC and supplied to an RF power amplifier (PA). As described in thepreceding section, in a polar loop system materializing EDGE system, atransmitter signal is separated into a phase component and an amplitudecomponent before respective feedback controls are performed with a phasemodulation control loop (PM LP) and an amplitude modulation control loop(AM LP), and a phase component and an amplitude component obtained afterthe feedback controls are combined by an RF power amplifier (PA).

As described in the preceding section, with TDMA (Time Division MultipleAccess) system, time slots can be set for or changed in setting to anidle state, an operation to receive a signal from a base station or anoperation to send a signal to the base station. Particularly, inswitching to a transmission operation time slot from another time slot,the intensity of an RF transmitter signal must be increased at anascending rate determined by GMSK standard. The increase of the RFtransmitter signal intensity of this time is termed “ramp-up”. When theascending rate of the ramp-up is larger than a value determined by GMSKstandard, the unwanted radiation is increased, causing an increase of anadjacent channel power leak ratio (ACPR). Reversely, in switching from atransmission operation time slot to another time slot, the intensity ofan RF transmitter signal must be decreased at a descending ratedetermined by GMSK standard. The decrease of the RF transmitter signalintensity of this time is termed “ramp-down”. When the descending rateof the ramp-down is larger than a value determined by GMSK standard, theunwanted radiation is increased, causing an increase of the adjacentchannel power leak ratio (ACPR). The ramp voltages for the ramp-up andramp-down are produced from digital ramp data from a baseband LSI.

On the on the hand, the intensity of an RF transmitter signal sent tothe base station from the communications terminal device must becontrolled in proportion to the communication distance between acommunications terminal device such as a mobile phone terminal and abase station. The intensity of an RF transmitter signal at the time ofcompletion of the rise of ramp-up is proportional to the communicationdistance between a communications terminal device and a base station.The voltage level of a ramp voltage produced by a baseband LSI at thetime of completion of ramp-up is proportional to the communicationdistance. In addition, the intensity of an RF transmitter signal to thebase station which has responded to the level of a ramp voltage from thebaseband LSI is controlled according to an amplification factor of theRF power amplifier (PA). The amplification factor (gain) of the RF poweramplifier (PA) can be controlled by an automatic power control voltage(Vapc).

As described above, in the polar loop system materializing the EDGEsystem, the phase modulation control loop (PM LP) and amplitudemodulation control loop (AM LP) each include an RF power amplifier (PA)in each loop. In GMSK, RF power amplifiers (PA) are required to generatean RF power of several watts, and therefore RF power amplifiers (PA)each incorporate a power amplification transistor such as a power MOSwith a large device size. As a result, the RF power amplifiers (PA) eachhave a large nonlinearity and a large phase delay, however phaseinformation and amplitude information of RF transmitter signals producedby the RF power amplifiers (PA) are exact because the two loops includeRF power amplifiers (PA) respectively.

On the other hand, for ramp-up and ramp-down in the EDGE transmissionmode, the amplification factor of the RF power amplifier (PA) includedin the amplitude modulation control loop (AM LP) must be controlleddepending on the ramp voltages or digital ramp data. However, it isrequired to make compensation so that the level of a feedback signal ofthe amplitude modulation control loop (AM LP) is not changed even whenthe amplification factor of the RF power amplifier (PA) included in theamplitude modulation control loop (AM LP) is changed. The technique isbecoming more sophisticated, and therefore the description thereof is tobe continued with reference to the drawings.

FIG. 1 is a diagram showing a transmitter which has been examined by theinventors prior to the invention. The transmitter includes: a basebandLSI (BB); an RF communication semiconductor integrated circuit (RF IC);a power-amplifier module PAM; an analog front-end module FEM; and anantenna ANT for receive and transmission. To the baseband LSI (BB), anapplication processor (AP), a static random access memory (SRAM), aflash non-volatile memory (Flash) are connected through external buses.In the flash non-volatile memory Flash, various kinds of controlprograms and application software programs for the baseband LSI,application processor AP and RF IC are stored.

Various commands from the baseband LSI to the RF IC, transmission data,various pieces of control data are supplied to a digital RF interface 1of the RF IC. An RF receive signal received through the antenna ANT forreceive and transmission is supplied to a receive system (not shown) ofthe RF IC through the analog front-end module FEM, and converted downinto an analog baseband receive signal. The analog baseband receivesignal is converted by an analog-to-digital converter into a digitalbaseband receive signal, and supplied to the baseband LSI through thedigital RF interface 1.

Also, a transmission digital baseband signal from the baseband LSI issupplied to the digital RF interface 1, and then to a digital modulator2. The digital modulator core in the digital modulator 2 responds to thetransmission digital baseband signal to produce orthogonal transmissiondigital baseband signals TxDBI and TxDBQ. Two digital-to-analogconverters (DAC) in the digital modulator 2 each convert the orthogonaltransmission digital baseband signals TxDBI and TxDBQ into orthogonaltransmission analog baseband signals TxABI and TxABQ, and then supplythe resultant analog signal to corresponding one of two mixers of atransmission mixer 3 respectively. The intermediate frequency localcarrier signals for transmission supplied to the two mixers of thetransmission mixer 3 are formed by dividing of an oscillation signal ofan RF voltage control oscillator 4 by a 1/N frequency divider and a ½frequency divider, and phase shift by a 90-degree phase shifter 5. Thetwo intermediate frequency local carrier signals for transmissionsupplied to the two mixers of the transmission mixer 3 from the90-degree phase shifter 5 have a 90-degree phase difference.Incidentally, the oscillation frequency of the RF voltage controloscillator 4 is set by an RF fractional PLL frequency synthesizer 6.Further, between an output of the RF voltage control oscillator 4 and aninput of the 1/N frequency divider is connected a buffer amplifier BF3.An intermediate-frequency transmitter signal Vref is formed by vectorsynthesis from the output of an adder connected with outputs of the twomixers of the transmission mixer 3. The intermediate-frequencytransmitter signal Vref is supplied to the phase modulation control loopPM LP and amplitude modulation control loop AM LP. In EDGE transmissionmode the phase modulation control loop PM LP makes the phases of RFtransmitter signals output from RF power amplifiers PA1 and PA2 of thepower-amplifier module PAM follow the phase of theintermediate-frequency transmitter signal Vref. The amplitude modulationcontrol loop AM LP makes the amplitudes of RF transmitter signals outputfrom the RF power amplifiers PA1 and PA2 of the power-amplifier modulePAM follow the amplitude of the intermediate-frequency transmittersignal Vref.

The phase modulation control loop PM LP includes a feed circuitconstituted by a phase comparator PD, a low-pass filter LF1, a voltagecontrol oscillator 7 for transmission, a switch SW4, a ½ frequencydivider, a buffer amplifier BF2, driver amplifiers DR1 and DR2 and apower-amplifier module PAM. The phase modulation control loop PM LPfurther includes a back circuit constituted by couplers Cp11 and Cp12,attenuators ATT1 and ATT2, a buffer amplifier BF1, a switch SW1, adown-conversion mixer DCM, and switches SW2 and SW3. The feed circuitand the back circuit form a feedback. In EDGE transmission mode, an RFcomponent of an RF transmitter signal from the power-amplifier modulePAM is supplied to one input terminal of the down-conversion mixer DCMthrough the couplers Cp11 and Cp12, the attenuators ATT1 and ATT2, thebuffer amplifier BF1, and the switch SW1. In GMSK transmission mode, anRF component coming from the output of the voltage control oscillator 7for transmission or the output of the ½ frequency divider is supplied tothe one input terminal of the down-conversion mixer DCM through thebuffer amplifier BF2 and the switch SW1. To the other input terminal ofthe mixer DCM, an oscillation signal from the RF voltage controloscillator 4 is supplied through two ½ frequency dividers and a switchSW6. As a result, an intermediate frequency amplitude feedback signalhaving the same phase and frequency as the phase and frequency of theintermediate-frequency transmitter signal Vref supplied to one inputterminal of the phase comparator PD from the transmission mixer 3 isproduced from the output of the mixer DCM. In EDGE transmission mode,the intermediate frequency amplitude feedback signal produced from theoutput of the mixer DCM will be supplied to the other input terminal ofthe phase comparator PD through the switch SW2, a first variableamplifier MVGA and the switch SW3. In GMSK transmission mode, theintermediate frequency amplitude feedback signal produced from theoutput of the mixer DCM is supplied to the other input terminal of thephase comparator PD through the switches SW2 and SW3.

The amplitude modulation control loop AM LP includes a feed circuitconstituted by an amplitude comparator AMD, a low-pass filter LF2, asecond variable amplifier IVGA, a voltage-current converter VIC, aswitch SW5, a level converter LVC and a power-amplifier module PAM. Theamplitude modulation control loop AM LP further includes a back circuitconstituted by the couplers Cp11 and Cp12, the attenuators ATT1 andATT2, the buffer amplifier BF1, the switch SW1, the down-conversionmixer DCM, the switch SW2 and the first variable amplifier MVGA. Thefeed circuit and the back circuit form a feedback. An RF component of anRF transmitter signal from the power-amplifier module PAM is supplied tothe one input terminal of the down-conversion mixer DCM. To the otherinput terminal of the mixer DCM, the oscillation signal from the RFvoltage control oscillator 4 is supplied through the two ½ frequencydividers and the switch SW6. As a result, an intermediate frequencyamplitude feedback signal having the same amplitude as that of theintermediate-frequency transmitter signal Vref supplied to one inputterminal of the amplitude comparator AMD from the transmission mixer 3will be produced from the output of the first variable amplifier MVGAand supplied to the other input terminal of the amplitude comparatorAMD. In GMSK transmission mode, the output of a voltage-currentconverter VID is supplied to an input of the level converter LVC of thefeed circuit through the switch SW5. To one input terminal of thevoltage-current converter VID is supplied an analog ramp voltage Vrampfrom a ramp digital-to-analog converter 8; to the other input terminalof the voltage-current converter VID is supplied the output of the levelconverter LVC. Therefore, in the GMSK transmission mode, the output ofthe level converter LVC supplied to the power-amplifier module PAM issubstantially identical to the analog ramp voltage Vramp from the rampdigital-to-analog converter 8.

Now, it is noted that in the EDGE transmission mode, the back circuit ofthe phase modulation control loop PM LP and the back circuit of theamplitude modulation control loop AM LP share the couplers Cp11 andCp12, the attenuators ATT1 and ATT2, the buffer amplifier BF1, theswitch SW1, the down-conversion mixer DCM, the switch SW2 and the firstvariable amplifier MVGA.

Also, an RF transmitter signal TxGSM850 of GSM850 substantially near 0.8GHz and an RF transmitter signal TxGSM900 of GSM900 substantially near0.9 GHz are produced from the output of the power amplifier PA1. An RFtransmitter signal TxDCS1800 of DCS1800 near about 1.8 GHz and an RFtransmitter signal TxPCS1900 of PCS1900 near about 1.9 GHz are producedfrom the output of the power amplifier PA2.

Before the description with reference to FIG. 1, it has been describedthat ramp-up and ramp-down in the EDGE transmission mode need control ofthe amplification factor of an RF power amplifier included in anamplitude modulation control loop AM LP in response to a ramp voltage ordigital ramp data. Also, it has been described that compensation must bemade so that the level of a feedback signal of the amplitude modulationcontrol loop AM LP is not changed even when the amplification factor ofthe RF power amplifier included in the amplitude modulation control loopAM LP is changed.

The two things can be materialized by controlling the gain of the firstvariable amplifier MVGA of the back circuit in the amplitude modulationcontrol loop AM LP in inverse proportion to the digital ramp data.Specifically, in ramp-up, digital ramp data is increased in order toincrease the intensity of an RF transmitter signal, which is the outputof the RF power amplifier. Then, the gain of the first variableamplifier MVGA of the back circuit in the amplitude modulation controlloop AM LP is lowered. However, it is required to maintain the level ofa feedback signal produced from the output of the first variableamplifier MVGA and supplied to the other input terminal of the amplitudecomparator AMD at the level of the signal Vref supplied to the one inputterminal of the amplitude comparator AMD from the transmission mixer 3without lowering the level of the feedback signal. To do so, it sufficesto increase the amplification factor of the RF power amplifier in adirection reverse to that of lowering of the gain of the first variableamplifier MVGA by a quantity equal to the absolute value of the quantityof the lowering. This enables the ramp-up and ramp-down in the EDGEtransmission mode, and therefore exact amplitude modulation in the EDGEtransmission mode can be achieved.

On the other hand, the gain of the second variable amplifier IVGA of thefeed circuit in the amplitude modulation control loop AM LP iscontrolled in direct proportion to digital ramp data. Consequently, evenwhen the digital ramp data is changed, the sum of the gains of the firstand second variable amplifiers MVGA and IVGA becomes substantiallyconstant. As a result, the effect of the increase in the digital rampdata making remarkably smaller the phase margin of open-loop frequencycharacteristics of the amplitude modulation control loop AM LP isreduced.

Meanwhile, as it has been becoming ubiquitous to use a digital interfacebetween an RF IC and a baseband LSI, a transmission baseband signal, areceive baseband signal and a ramp voltage between them have been alsochanged from analog signals to digital ones. Hence, thedigital-to-analog converter incorporated in the RF IC converts a digitalsignal like this into an analog signal and supplies the resultant signalto a circuit inside the RF IC. In the analog interface age beforedigital interfaces, digital ramp data produced in a baseband LSI hadbeen converted to analog ramp voltages by a built-in rampdigital-to-analog converter (RampDAC) of a baseband LSI. Therefore, ananalog ramp voltage from the built-in ramp digital-to-analog converterof the baseband LSI had been supplied to an RF IC through a conductorline of a circuit board outside a chip. The analog ramp voltage wasformed by a linearizer circuit provided in the RF IC to control gains ofthe first and second variable amplifiers MVGA and IVGA, therebymaterializing a continuously changing gain. When the gain control isperformed continuously in this way, no switching noise arises when thegains of the RF power amplifiers PA1 and PA2 are changed.

On the other hand, with widespread use of digital interfaces, rampdigital-to-analog converters (RampDAC) for converting digital ramp datato analog ramp voltages ended up being relocated to the inside of RF ICsfrom the inside of baseband LSIs together with other digital-to-analogconverters and analog-to-digital converters. However, to control thegains of the first and second variable amplifiers MVGA and IVGA by useof a conventional analog ramp voltage, it is required to incorporate alinearizer circuit in an RF IC. This is unfavorable in terms of the costand performance when considering of the area of an RF IC chip and theelectric current consumption thereof. Hence, a gain variable amplifierof a digital type has been adopted, which uses not an analog rampvoltage having undergone the processing by a ramp digital-to-analogconverter, but a digital control signal resulting from decode of digitalramp data for control of the gains of the first and second variableamplifiers MVGA and IVGA.

In GMSK transmission mode of the RF IC of the transmitter of FIG. 1, thechange in the analog ramp voltage Vramp, which is an output of the rampdigital-to-analog converter 8 incorporated in the RF IC is sharp. Suchsharp change in the analog ramp voltage Vramp is supplied to thepower-amplifier module PAM through the voltage-current converter VID,the switch SW5 and the level converter LVC. A voltage converter LDO ofthe power-amplifier module PAM responds to a sharp change of the analogramp voltage Vramp to produce an automatic power control voltage Vapchaving a relatively sharp change. However, the RF power amplifiers PA1and PA2 of the power-amplifier module PAM are controlled continuouslywith an analog ramp voltage, and therefore the switching noise owing tothe switching of circuits inside the RF IC or the like is not generated.Thus, as for the RF power amplifiers PA1 and PA2, the changes in gainsof the RF power amplifiers PA1 and PA2 never cause the change in theintensity of the RF transmitter signal at a rate over the rate of GMSKstandard in the GMSK transmission mode even when the automatic powercontrol voltage Vapc is changed relatively sharply.

The ramp control in the EDGE transmission mode of the RF IC of thetransmitter of FIG. 1 is achieved by controlling the gain of the firstvariable amplifier MVGA of the back circuit of the amplitude modulationcontrol loop AM LP in inverse proportion to digital ramp data.Specifically, in ramp-up, digital ramp data is increased in order toincrease the intensity of an RF transmitter signal, which is the outputof the RF power amplifier. Then, the gain of the first variableamplifier MVGA of the back circuit in the amplitude modulation controlloop AM LP is lowered. However, it is required to maintain the level ofa feedback signal produced from the output of the first variableamplifier MVGA and supplied to the other input terminal of the amplitudecomparator AMD at the level of the signal Vref supplied to the one inputterminal of the amplitude comparator AMD from the transmission mixer 3without lowering the level of the feedback signal. To do so, it sufficesto increase the amplification factor of the RF power amplifier in adirection reverse to that of lowering of the gain of the first variableamplifier MVGA by a quantity equal to the absolute value of the quantityof the lowering. Hence, for the purpose of reducing the area of the RFIC chip and lowering the power consumption thereof, the first and secondvariable amplifiers MVGA and IVGA are constituted by two or moredifferential amplifiers and others; the differential amplifiers arecontrolled to be activated or deactivated according to the settings oftheir gains. However, as a result of this arrangement, it has beenrevealed that when the gains of the amplifiers are switched with aminimum gain change width (e.g. 0.2 dB) at a high speed, switching noiseis caused, and the intensity of the RF transmitter signal is changed ata rate over the rate of GMSK standard.

Further, the inventors found that in the EDGE transmission mode, theintensity of the RF transmitter signal was changed at a rate over therate of GMSK standard for another cause.

The cause is the error of the change in gain of the first variableamplifier MVGA of the back circuit of the amplitude modulation controlloop AM LP resulting from the manufacturing error of a semiconductorchip in association with the RF IC. In other words, the cause was thatthe manufacturing error of a semiconductor chip in association with theRF IC makes uneven the quantity of the change in gain of the firstvariable amplifier MVGA of the amplitude modulation control loop AM LPdepending on the step of the change in digital ramp data.

FIG. 2 is a diagram showing a structure of the first variable amplifierMVGA of the amplitude modulation control loop AM LP of the RF IC of thetransmitter shown in FIG. 1.

The first variable amplifier MVGA includes a first amplifier AMP1, asecond amplifier AMP2 and a third amplifier AMP3, which are connecteddependently. The gain-controllable range of the first amplifier AMP1 isbetween 6 and 30 dB, that of the second amplifier AMP2 is between 0 and26 dB, and that of the third amplifier AMP3 is between −2 and 0 dB. Thewidth of change of gain of the first and second amplifiers AMP1 and AMP2is 2 dB/step, and the width of change of gain of the third amplifierAMP3 is 0.2 dB/step.

When eight-bit digital ramp data MVGA_IN [7:0] input to the controllerMVGA Gain Cont is decoded, three sets of digital data for setting thegains of the first, second and third amplifiers AMP1, AMP2 and AMP3 arecreated.

Thirteen bits of the first set of digital data are used to individuallyactivate or deactivate thirteen parallel amplifiers included in thefirst amplifier AMP1. Fourteen bits of the second set of digital dataare used to individually activate or deactivate fourteen parallelamplifiers included in the second amplifier AMP2. Eleven bits of thethird set of digital data are used to individually activate ordeactivate eleven parallel amplifiers included in the third amplifierAMP3. To an output of the third amplifier AMP3 is connected a low-passfilter LPF which reduces harmonics of an intermediate-frequency feedbacksignal with a frequency of about 80 MHz to be supplied to the amplitudecomparator AMD when the feedback signal goes through.

Also, to the controller MVGA Gain Cont, a clock signal CLK of 26 MHz anda reset signal RST for resetting eight-bit digital ramp data MVGA_IN[7:0] are supplied from the digital RF interface 1.

FIGS. 3A and 3B are plots each showing quantities of change of gain ofthe first variable amplifier MVGA in response to the change stepaccording to the eight-bit digital ramp data MVGA_IN [7:0] supplied tothe controller MVGA Gain Cont as in FIG. 2.

FIG. 3A shows an ideal condition that involves no error in manufactureof a RF IC semiconductor chip. In the case of FIG. 3A, the quantities ofchange of gain of the first variable amplifier MVGA in response to theminimum change step according to the eight-bit digital ramp data MVGA_IN[7:0] become a uniform value of 0.2 dB.

In contrast, FIG. 3B shows a practical condition that involves an errorin manufacture of a RF IC semiconductor chip. In the case of FIG. 3B,the most of the quantities of change of gain of the first variableamplifier MVGA in response to the minimum change step according to theeight-bit digital ramp data MVGA_IN [7:0] is distributed between 0.17and 0.23 dB. However, there are quite a few points showing a gain changequantity of 0.25 dB, and one of them shows a remarkably large quantityof the change as large as 0.32 dB.

Therefore, the case where an operation of ramp-up is performed in apractical condition that involves an error in manufacture of a RF ICsemiconductor chip as described with reference to FIG. 3B is assumed,for example. Even when the eight-bit digital ramp data MVGA_IN [7:0] isincreased by the minimum change step at a fixed rate, there arises apoint where an error largely decreases the gain of the first variableamplifier MVGA. At this point, the intensity of the RF transmittersignal from the power amplifier ends up being increased largely over theset gain. In contrast, in the case of ramp-down, even when the eight-bitdigital ramp data MVGA_IN [7:0] is decreased by the minimum change stepat a fixed rate, there arises a point where an error largely increasesthe gain of the first variable amplifier MVGA. At this point, theintensity of the RF transmitter signal form the power amplifier ends upbeing decreased largely over the set gain. As a result, unwantedradiation is increased, and thus the adjacent channel power leak ratio(ACPR) is increased.

The invention was made as a result of examination made by the inventorsprior to the present invention as described above. Therefore, it is anobject of the invention to lower the level of unwanted radiation inramp-up of an RF transmitter signal of the RF power amplifier, which issupplied to an antenna. Also, it is another object of the invention tolower the level of unwanted radiation in ramp-down of the RF transmittersignal of the RF power amplifier supplied to the antenna.

The above and other objects of the invention and novel features hereofwill be apparent from the description hereof and the accompanyingdrawings.

Of the embodiments disclosed herein, the preferred ones will bedescribed below in brief.

That is, as to a transmitter according to a preferred embodiment of theinvention, an internal operation in the transmitter is adjusted so thatthe level of the RF transmitter signal of the RF power amplifiersupplied to the antenna is substantially stopped from rising, or made todescend in course of ramp-up of the RF transmitter signal. In regard toa transmitter according to another preferred embodiment of theinvention, an internal operation in the transmitter is adjusted so thatthe level of the RF transmitter signal of the RF power amplifiersupplied to the antenna is substantially stopped from going down, ormade to ascend in course of ramp-down of the RF transmitter signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a transmitter which has been examined by theinventors prior to the invention, however it is identical in basicstructure to a transmitter according to an embodiment of the invention;

FIG. 2 is a diagram showing a structure of a first variable amplifier ofan amplitude modulation control loop of an RF IC of the transmittershown in FIG. 1;

FIGS. 3A and 3B are plots each showing quantities of change of gain ofthe first variable amplifier in response to the change step according todigital ramp data supplied to the controller as shown in FIG. 2;

FIG. 4 is a time chart of assistance in explaining an operation sequenceof the transmitter according to the embodiment of the invention shown inFIG. 1 in the EDGE transmission mode;

FIG. 5 is an illustration of assistance in explaining the detail ofeffective data of transmission data of the operation sequence shown withreference to FIG. 4;

FIG. 6 is a time chart of assistance in explaining details of anoperation sequence before and after an elapse of the setting time duringthe time of ramp-up in the EDGE transmission mode shown in FIG. 4;

FIG. 7 is a plot of assistance in explaining the effect of the reductionin unwanted radiation by the ramp-up operation sequence of thetransmitter according to the embodiment of the invention shown in FIG. 1in the EDGE transmission mode;

FIG. 8 is a time chart of assistance in explaining details of anoperation sequence in ramp-down in the EDGE transmission mode shown inFIG. 4;

FIG. 9 is a plot of assistance in explaining the effect of the reductionin unwanted radiation by the ramp-down operation sequence of thetransmitter according to the embodiment of the invention shown in FIG. 1in the EDGE transmission mode;

FIG. 10 is a time chart of assistance in explaining an operationsequence in the case of switching GMSK transmission mode to EDGEtransmission mode;

FIG. 11 is a time chart of assistance in explaining an operationsequence in the case of switching the EDGE transmission mode to the GMSKtransmission mode;

FIG. 12 is a time chart of assistance in explaining an operationsequence in the case of switching the GMSK transmission mode of accessburst to the EDGE transmission mode of normal burst;

FIG. 13A is a plot showing RF transmission spectra obtained by aconventional common transmitter which performs ramp-up and ramp-down inthe EDGE transmission mode;

FIG. 13B is a plot showing RF transmission spectra achieved by thetransmitter according to the embodiment of the invention shown in FIG.1;

FIG. 14 is a diagram showing a transmitter according to anotherembodiment of the invention, which adopts the polar modulator system andsupports the EDGE transmission mode;

FIG. 15 is a diagram showing the RF IC according to the embodiment ofthe invention more specifically; and

FIG. 16 is a block diagram showing a structure of a mobile phoneincorporating an RF IC, a baseband LSI, a power-amplifier module, ananalog front-end module and attenuators according to an embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 1. Summary of thePreferred Embodiments

First, the summary of the preferred embodiments of the inventiondisclosed herein will be described. In the description of Summary of thepreferred embodiments, reference characters and signs to refer to thedrawings, which are accompanied with paired round brackets, justexemplify what the concepts of components referred to by the charactersand signs contain.

[1] A transmitter according to a preferred embodiment of the inventionincludes RF power amplifiers (PA1, PA2) which produce an RF transmittersignal to be supplied to an antenna, and an RF transmittersignal-processing circuit (RF IC) which converts up a basebandtransmitter signal thereby to produce an RF transmitter input signal tobe supplied to the RF power amplifier.

An internal operation of the RF transmitter signal-processing circuit isadjusted so that the level of the RF transmitter signal is substantiallystopped from rising, or made to descend in course of ramp-up of the RFtransmitter signal.

In the transmitter according to a preferable form, an internal operationof the RF transmitter signal-processing circuit is adjusted so that thelevel of the RF transmitter signal is substantially stopped from goingdown, or made to ascend in course of ramp-down of the RF transmittersignal.

In the transmitter according to a more preferable form, adjustment ofthe internal operation of the RF transmitter signal-processing circuitin course of ramp-up is enabled by ramp-up adjustment data (Last 4symbols) contained in preamble data (Preamble_Data) precedent to realtransmission data (Tr_Data) to be transmitted after completion of theramp-up (see FIGS. 5, 6 and 7).

In an example, the ramp-up adjustment data and the real transmissiondata are supplied from a baseband processing unit (BB LSI).

In the transmitter according to a more preferable form, adjustment ofthe internal operation of the RF transmitter signal-processing circuitin course of ramp-down is enabled by ramp-down adjustment data (First 4symbols) contained in dummy data (Dummy 8 symbols) added to the realtransmission data (see FIGS. 5, 8 and 9).

In another example, the ramp-down adjustment data is also supplied fromthe baseband processing unit.

In the transmitter according to a specific form, the RF transmittersignal-processing circuit includes a phase modulation control loop (PMLP) and an amplitude modulation control loop (AM LP), which produce theRF transmitter input signal through phase modulation and amplitudemodulation respectively. The amplitude modulation control loop includesa first variable amplifier (MVGA) in its loop; the gain of the firstvariable amplifier is changed according to ramp information (Ramp_UpData, Ramp_Down Data) for the ramp-up and ramp-down. Thus, the ramp-upand ramp-down are enabled by controlling the gain of the first variableamplifier according to the ramp information.

In the transmitter according to a more specific form, the amplitudemodulation control loop includes a second variable amplifier (IVGA) inits loop; the gain of the second variable amplifier is changed in adirection reverse to that of the change of the gain of the firstvariable amplifier in response to the ramp information.

In the transmitter according to the most specific form, the amplitudemodulation control loop constitutes one of a polar loop for EDGEtransmission and a polar modulator.

[2] An RF transmitter signal-processing circuit (RF IC) according toanother aspect is arranged so as to be connected with RF poweramplifiers (PA1, PA2) which produce an RF transmitter signal to besupplied to the antenna of the transmitter.

The RF transmitter signal-processing circuit converts up the basebandtransmitter signal thereby to produce an RF transmitter input signal tobe supplied to the RF power amplifier.

An internal operation of the RF transmitter signal-processing circuit isadjusted so that the level of the RF transmitter signal is substantiallystopped from rising, or made to descend in course of ramp-up of the RFtransmitter signal.

[3] An method for operating the transmitter according to another aspectincludes a preparation step of preparing RF power amplifiers (PA1, PA2)which produce an RF transmitter signal to be supplied to the antenna,and an RF transmitter signal-processing circuit (RF IC) which convertsup a baseband transmitter signal thereby to produce an RF transmitterinput signal to be supplied to the RF power amplifier.

The operating method includes a ramp-up adjustment step of adjusting aninternal operation of the RF transmitter signal-processing circuit sothat the level of the RF transmitter signal is substantially stoppedfrom rising, or made to descend in course of ramp-up of the RFtransmitter signal.

The operating method includes a ramp-up step of making the RFtransmitter signal ramp up after the ramp-up adjustment step.

The operating method according to a preferable form includes a ramp-downadjustment step of adjusting an internal operation of the RF transmittersignal-processing circuit so that the level of the RF transmitter signalis substantially stopped from going down, or made to ascend in course oframp-down of the RF transmitter signal.

The operating method includes a ramp-down step of making the RFtransmitter signal ramp down after the ramp-down adjustment step.

In the operating method according to a preferable form, the ramp-upadjustment step, the ramp-up step, the ramp-down adjustment step, andthe ramp-down step are controlled by software programs stored in anon-volatile storage device contained in the transmitter.

2. Further Detailed Description of the Preferred Embodiments

Next, the embodiments will be described further in detail. The detaileddescription of the best mode of carrying out the invention will bepresented below with reference to the drawings. In all the drawings towhich reference is made in describing the best mode of carrying out theinvention, the members having a common function are identified by acommon reference character or sign, and the description thereof isskipped herein.

<<Configuration of the Transmitter>>

FIG. 1 is a diagram showing a transmitter according to an embodiment ofthe invention. FIG. 2 is a diagram showing a structure of a firstvariable amplifier MVGA of an amplitude modulation control loop AM LP ofan RF IC of the transmitter shown in FIG. 1.

The transmitter shown in FIG. 1 has no large difference in appearancefrom a transmitter, which had been examined prior to the invention.However, the transmitter in association with the invention differs fromthe conventional one in function.

Specifically, in the transmitter according to the embodiment of theinvention shown in FIG. 1, an internal operation in the transmitter isadjusted so that the level of the RF transmitter signal is substantiallystopped from rising, or made to descend in course of ramp-up of the RFtransmitter signal of the RF power amplifier to be supplied to theantenna. The waveform illustration of FIG. 7 shows a way of the leveldown of the RF transmitter signal in course of ramp-up. According to aspecific embodiment, adjustment of the internal operation can be made bya digital baseband transmitter signal produced by the baseband LSI.

Further, in the transmitter according to the embodiment of the inventionshown in FIG. 1, an internal operation in the transmitter is adjusted sothat the level of the RF transmitter signal is substantially stoppedfrom going down, or made to ascend in course of ramp-down of the RFtransmitter signal of the RF power amplifier to be supplied to theantenna. The waveform illustration of FIG. 9 shows a way of the rise ofthe level in course of ramp-down of the RF transmitter signal. Accordingto the specific embodiment, adjustment of the internal operation can bemade by a digital baseband transmitter signal produced by the basebandLSI.

<<Transmission Operation by the Transmitter in Edge Transmission Mode>>

FIG. 4 is a time chart of assistance in explaining an operation sequenceof the transmitter according to the embodiment of the invention shown inFIG. 1 in the EDGE transmission mode.

<<Transmission Data Upload Command>>

Now, reference is made to FIG. 4. At the time T1 a transmission dataupload command Tx_data Up_Load is transferred to the RF IC from thebaseband LSI, and transmission data Tx_Data of the digital basebandtransmitter signal is also transferred. The transmission data Tx_Data iseffective data Eff_D of 168 symbols, and held in a built-in RAM of thedigital RF interface 1 of the RF IC or an internal memory such as a dataregister thereof. The detail of effective data Eff_D of 168 symbols oftransmission data Tx_Data transferred at the time T1 is shown in FIG. 5.

<<Effective Data of Transmission Data>>

FIG. 5 is an illustration showing the detail of 168 symbols of effectivedata Eff_D of transmission data Tx_Data transferred in the form of anormal burst from the baseband LSI to the RF IC. The 168 symbols ofeffective data Eff_D are composed of twelve symbols of dummy (preambledata) and 156 symbols of time slot (normal burst). In this embodiment ofthe invention, particularly the last four symbols of the twelve symbolsof dummy (preamble data) contain control data for reduction in unwantedradiation important for ramp-up. Incidentally, the 156 symbols of timeslot (normal burst) contain a tail bit of the first three symbols and atail bit of the last three symbols, and 142 symbols of transfer dataTr_Data between them, which can be utilized in actual transmission.Further, in this embodiment of the invention, the first four symbols ofthe last-added eight symbols of dummy of the 168 symbols of effectivedata Eff_D contain control data for reduction in unwanted radiationimportant for ramp-down. In addition, the 142 symbols of transfer dataTr_Data located halfway contain a digital baseband transmitter signal.

In GSM data communication, one symbol of a transmission-and-receivebaseband signal consists of four bits. When the last fourth bit of asymbol is “1”, the signal is a piece of EDGE transmission data, and thefirst three bits show an amplitude according to AM modulation. When thelast fourth bit of a symbol is “0”, the signal is a piece of GMSKtransmission data, which only phase modulation is applied to. The firstthree bits of such data are, for example, all “1”, i.e. “111”, and inthat case, the signal is fixed in amplitude. In addition, in GSM datacommunication, of four bits of a symbol, one bit is termed a quarterbit. Further, in the case of using a system clock frequency of 26 MHz,one quarter bit (1 Qb) shows a time of 923.08 nanoseconds.

<<EDGE Transmission Mode>>

When the RF IC of the transmitter according to the embodiment of theinvention shown in FIG. 1 responds to the setting of RF IC operationmode transferred from the baseband LSI to bring the transmitter intoEDGE transmission mode, the feed circuit of the amplitude modulationcontrol loop AM LP is activated to feed amplitude modulationinformation. Now, it is noted that the feed circuit of the amplitudemodulation control loop AM LP includes the amplitude comparator AMD, thelow-pass filter LF2, the second variable amplifier IVGA, thevoltage-current converter VIC, the switch SW5, the level converter LVC,and the power-amplifier module PAM. Also, the back circuit of theamplitude modulation control loop AM LP is activated to back theamplitude modulation information. Now, it is noted that the back circuitof the amplitude modulation control loop AM LP includes the couplersCp11 and Cp12, the attenuators ATT1 and ATT2, the buffer amplifier BF1,the switch SW1, the down-conversion mixer DCM, the switch SW2, and thefirst variable amplifier MVGA. As a matter of course, the feed and backcircuits of the phase modulation control loop PM LP are activated tofeed and back phase modulation information respectively. Now, it isnoted that the feed circuit of the phase modulation control loop PM LPincludes the phase comparator PD, the low-pass filter LF1, the voltagecontrol oscillator 7 for transmission, the switch SW4, the ½ frequencydivider, the buffer amplifier BF2, the driver amplifiers DR1 and DR2 andthe power-amplifier module PAM. Further, the back circuit of the phasemodulation control loop PM LP includes the couplers Cp11 and Cp12, theattenuators ATT1 and ATT2, the buffer amplifier BF1, the switch SW1, thedown-conversion mixer DCM, the switches SW2 and SW3, and the firstvariable amplifier MVGA.

<<GMSK Transmission Mode>>

When the RF IC of the transmitter according to the embodiment of theinvention shown in FIG. 1 responds to the setting of RF IC operationmode transferred from the baseband LSI to bring the transmitter intoGMSK transmission mode, in which only phase modulation is used, the feedand back circuits of the phase modulation control loop PM LP areactivated to feed and back phase modulation information respectively. Incontrast, in the GMSK transmission mode, the amplitude modulation is notperformed, and therefore the feed and back circuits of the amplitudemodulation control loop AM LP are deactivated. Thus, in the GMSKtransmission mode, the power consumption of the feed and back circuitsof the amplitude modulation control loop AM LP can be trimmed down.

<<Transmission Mode On Command>>

Reference is made to FIG. 4. At the time T2 a transmission mode oncommand Tx_Mode ON is transferred from the baseband LSI to the RF IC.Then, operations of the digital modulator 2, transmission mixer 3, RFvoltage control oscillator 4, RF frequency synthesizer 6, voltagecontrol oscillator 7 for transmission, and two modulation control loopsPM LP and AM LP are started. The analog baseband transmitter signalsTxABI and TxABQ from the two digital-to-analog converters DAC of thedigital modulator 2 are raised to a predetermined DC voltage level shownby a waveform in FIG. 4. The predetermined DC voltage level of theanalog baseband transmitter signals TxABI and TxABQ can be used forcalibration of the DC offset cancel of paths between outputs of thedigital-to-analog converters DAC of the RF IC and inputs of thetransmission mixer 3. In addition, a power amplifier activation signalPA_ON for starting supply of source and bias voltages to the RF poweramplifiers PA1 and PA2 of the power-amplifier module PAM is also changedfrom Low level to High level.

<<Transmission Data Internal Transfer Command>>

Again, reference is made to FIG. 4. At the time T3 a transmission datainternal transfer command Tx_Data ON is transferred to the RF IC fromthe baseband LSI. When a predetermined delay time Delay has elapsed fromthe time T3, readout of 168 symbols of effective data Eff_D oftransmission data Tx_Data held by an internal memory such as a RAM ordata register incorporated in the RF IC is started. However, until asetting time, which is to be described later, has elapsed, the analogbaseband signals TxABI and TxABQ corresponding to the DC voltage aresupplied. After the setting time has elapsed, analog baseband signalsTxABI and TxABQ corresponding to the symbols are supplied. That is, asto eight symbols contained in twelve symbols (preamble data) before lastfour symbols of a dummy, four bits of each symbol are arranged to be all“1”, namely “1111”. This means that the value of amplitude resultingfrom AM modulation is an RMS value with a large constant amplitude inthe EDGE transmission mode. Now, it is noted that RMS is theabbreviation which stands for “Root Mean Square”. Thus, a digitalbaseband transmitter signal corresponding to the RMS amplitude value isread out from an internal memory such as a built-in RAM or data registerof the digital RF interface 1 of the RF IC, and supplied to the digitalmodulator 2. The digital modulator 2 produces orthogonal digitalbaseband transmitter signals TxDBI and TxDBQI. Then, orthogonal analogbaseband transmitter signals TxABI and TxABQ corresponding to the directvoltages are produced by the digital-to-analog converters, and suppliedto the transmission mixer 3. Thus, supply of the intermediate-frequencytransmitter signal Vref corresponding to the RMS value with a largeconstant amplitude to inputs of the phase modulation control loop PM LPand amplitude modulation control loop AM LP of the RF IC is started.

<<Ramp-Up Start Command>>

Now, reference is made to FIG. 4. At the time T4 a ramp-up start commandRamp_Up Start is transferred to the RF IF from the baseband LSI. Then,load of digital ramp data Ramp_Up Data for ramp-up into an internalmemory such as a built-in RAM or data register of the RF IC from thebaseband LSI is started. Therefore, as the digital value of the loadeddigital ramp data Ramp_Up Data is increased, the gain of the firstvariable amplifier MVGA of the amplitude modulation control loop AM LPof the RF IC is lowered. Reversely to this, the level of the automaticpower control voltage Vapc is raised, and the amplification factors ofthe RF power amplifiers PA1 and PA2 of the power-amplifier module PAMstart increasing. When the rise in the level of the automatic powercontrol voltage Vapc is started, the level of a control signal FEM_CONTfor activating the analog front-end module FEM is changed from Low toHigh. Then, supply of the RF transmitter signals to the antenna ANT fromthe RF power amplifiers PA1 and PA2 of the power-amplifier module PAMare started.

<<Level Down of Transmitter Signal in Course of Ramp-Up>>

When the setting time as mentioned above has elapsed in course of theincrease in the amplification factors of the RF power amplifiers PA1 andPA2 of the power-amplifier module PAM, supply of analog baseband signalsTxABI and TxABQ corresponding to the symbols is started. That is,readout of 168 symbols of effective data Eff_D as shown in FIG. 5 isexecuted. In this embodiment of the invention, of twelve symbols ofdummy, particularly the last four symbols contain control data for thereduction in unwanted radiation, which is important for ramp-up.Specifically, as to the last four symbols of twelve symbols of dummy(preamble data), four bits of each symbol are arranged to be e.g.“1101”, “1001”, “0011” and “1111”. This means that in the EDGEtransmission mode, the amplitude value resulting from amplitudemodulation of continuous transmitter signals by successive symbolsprovides a smaller amplitude in comparison to the RMS amplitude valuewhich offers a large constant amplitude. As a result, a digital basebandtransmitter signal representing a small amplitude value is read out fromthe internal memory such as a built-in RAM or data register of thedigital RF interface 1 of the RF IC, and supplied to the digitalmodulator 2. Then, the digital modulator 2 produces orthogonal digitalbaseband transmitter signals TxDBI and TxDBQ, and the orthogonal analogbaseband transmitter signals TxABI and TxABQ are produced by thedigital-to-analog converters and supplied to the transmission mixer 3.Thus, supply of the intermediate-frequency transmitter signal Vrefcorresponding to the small amplitude value of the phase modulationcontrol loop PM LP and amplitude modulation control loop AM LP of the RFIC is started. As a result, before and after an elapse of the settingtime during the time of ramp-up, the amplitude level of the RFtransmitter input signal supplied to the inputs of the RF poweramplifiers PA1 and PA2 of the power-amplifier module PAM from the feedcircuit of the phase modulation control loop PM LP of the RF IC ischanged from an RMS amplitude value offering a large constant amplitudeto a small amplitude value. Thus, according to the embodiment of theinvention, it is possible to reduce unwanted radiation important forramp-up, during which the amplification factors of the RF poweramplifiers PA1 and PA2 are increased.

The level down of the transmitter signal in course of ramp-up asdescribed above is performed in adjustment of the last four symbols ofdata of the dummy (preamble) of the effective data Eff_D of thetransmission data Tx_Data transferred to the RF IC from the basebandLSI, which has been shown in FIG. 5. The effective data Eff_D containingthe dummy (preamble) can be created by a control program stored in anexternal non-volatile memory such as a non-volatile memory in thebaseband LSI or a flash EEPROM memory incorporated in a mobile phone.

Also, the level down of the transmitter signal in course of ramp-up canbe performed in the RF IC by means of another method. Basically, theeffective data Eff_D containing a dummy (preamble) is produced in thebaseband LSI, and transferred to the RF IC. However, transfer data of aportion lowered in level in course of ramp-up, which comes from thebaseband LSI, is masked by a data correction circuit in the RF IC. Thedata correction circuit inserts a correction transmitter signal forlevel down of the transmitter signal in the masked portion, instead. Thecontrol of the signal masking and insertion can be performed by acontrol program stored in a non-volatile memory in the RF IC or anexternal non-volatile memory such as a flash EEPROM memory incorporatedin a mobile phone.

<<Sending of Real Transmission Data after Completion of Ramp-Up>>

Reference is made to FIG. 4, here. Between completion of ramp-up at thetime T5 and start of ramp-down at the time T6, transmission of a totalof 148 symbols consisting of a tail bit of the first three symbols, atail bit of the last three symbols, and transfer data Tr_Data of 142symbols between them, which can be used in actual transmission isperformed.

<<Ramp-Down Start Command>>

Now, reference is made to FIG. 4. At the time T6 a ramp-down startcommand Ramp_Down Start is transferred to the RF IC from the basebandLSI. Then, an internal operation sequence similar to the internaloperation sequence of the RF IC between the time T4 and time T5 isexecuted between the time T6 and time T7. Thus, it is possible to reduceunwanted radiation important for ramp-down, during which theamplification factors of the RF power amplifiers PA1 and PA2 aredecreased.

<<Detail of the Ramp-Up Operation Sequence>>

FIG. 6 is a time chart of assistance in explaining details of anoperation sequence before and after an elapse of the setting time duringthe time of ramp-up in the EDGE transmission mode shown in FIG. 4.

The setting time is set by the sum of a transmission delay time Tx-Delayand a transmission timing offset Timing-offset. The transmission delaytime Tx-Delay, which starts at the time T2 when the transmission mode oncommand Tx_Mode ON is transferred to the RF IC from the baseband LSI, isset to 72 microseconds in this example. The transmission timing offsetTiming-offset, which starts after the transmission delay time Tx-Delayhas elapsed, is set to 15 microseconds, in this example.

When a predetermined delay time Delay (corresponding to 18 Qb) haselapsed from the time T3 at which the transmission data internaltransfer command Tx_Data ON is transferred to the RF IC from thebaseband LSI, readout of straight 1's symbols, namely “1111” symbols ofthe first half portion of twelve symbols is executed. As a result, adigital baseband transmitter signal corresponding to an RMS amplitudevalue with a large constant amplitude is read out from the internalmemory such as a built-in RAM or data register of the digital RFinterface 1 of the RF IC. Hence, the analog baseband transmitter signalsTxABI and TxABQ form analog signals corresponding to the RMS amplitudevalue with a large constant amplitude.

At the time T4, the ramp-up start command Ramp_Up Start is transferredto the RF IC from the baseband LSI. Then, load of the digital ramp dataRamp_Up Data for ramp-up into the internal memory of the digital RFinterface 1 is started, and the supply to the first and second variableamplifiers MVGA and IVGA is performed. The digital ramp data Ramp_UpData for ramp-up consists of 16 pieces of data. The first eight piecesof data take on the data value “0”, and therefore the amplificationfactors of the RF power amplifiers PA1 and PA2 of the power-amplifiermodule PAM are set to be minimum.

The setting time elapses during the time of the first eight pieces ofdata being the data value “0”. As a result, the last four symbols of thetwelve symbols of dummy (preamble data) of the 168 symbols of effectivedata Eff_D and the three symbols before them are read out (see FIG. 5).The four bits of each of the last four symbols are “1101”, “1001”,“0011” and “1111”. This means that the amplitude value of continuoustransmitter signals resulting from AM modulation using successivesymbols offers a smaller amplitude in comparison to the RMS amplitudevalue with a large constant amplitude. As a result, a digital basebandtransmitter signal corresponding to the small amplitude value is readout from the internal memory such as a built-in RAM or data register ofthe digital RF interface 1 of the RF IC, and supplied to the digitalmodulator 2. Hence, the analog baseband transmitter signals TxABI andTxABQ have waveforms of an intermediate-amplitude value or a smallamplitude value. In this way, it is possible to reduce unwantedradiation important for ramp-up, during which the amplification factorsof the RF power amplifiers PA1 and PA2 are increased.

Now, the setting is made so that when five microseconds elapses from thetransmission timing offset Timing-offset, the automatic power controlvoltage Vapc is raised in response to the digital ramp data Ramp_UpData. Also, the setting is made so that at the time when a length oftime of 16 Qb has elapsed after the start of ramp-up at the time T4, thecontrol signal FEM_CONT for activating the analog front-end module FEMis changed in level from Low to High.

<<Reduction in Unwanted Radiation During Ramp-Up>>

FIG. 7 is a plot of assistance in explaining the effect of the reductionin unwanted radiation by the ramp-up operation sequence of thetransmitter according to the embodiment of the invention shown in FIG. 1in the EDGE transmission mode. In GMSK standard, it is defined that inramp-up, the increase in the RF transmitter signal from each RF poweramplifier varies between the characteristic curves L1 and L2. Thecharacteristic curve L_rp_cnv shows a conventional common ramp-upcharacteristic. Particularly, as to a portion strong in signal intensitydrawn by a broken line, the intensity of the RF transmitter signal canbe changed at a rate over the GMSK standard rate owing to switchingnoise caused at switching circuits in the RF IC, or the manufacturingerror of a semiconductor chip.

The characteristic curve L_rp_inv shows the ramp-up characteristicachieved by the embodiment of the invention shown in FIG. 1. Theintensity of the RF transmitter signal of the portion of theconventional common ramp-up characteristic curve L_rp_cnv drawn by thebroken line is adjusted. As a result, the risk of the intensity of theRF transmitter signal being changed at a rate over the GMSK standardrate owing to switching noise caused at switching circuits in the RF IC,or the manufacturing error of a semiconductor chip is reduced.

<<Detail of the Ramp-Down Operation Sequence>>

FIG. 8 is a time chart of assistance in explaining details of anoperation sequence in ramp-down in the EDGE transmission mode shown inFIG. 4.

At the time T6, the ramp-down start command Ramp_Down Start istransferred to the RF IC from the baseband LSI. Then, load of digitalramp data Ramp_Down Data for ramp-down into the internal memory of thedigital RF interface 1 from the baseband LSI is started, and the supplyto the first variable amplifier MVGA and the second variable amplifierIVGA is performed. The digital ramp data Ramp_Down Data for ramp-downconsists of 16 pieces of data. As data values of the first eight piecesof data descend as “1023”, “1010”, “900”, “700” and so on, theamplification factors of the RF power amplifiers PA1 and PA2 of thepower-amplifier module PAM are also decreased gradually.

Readout of the first four symbols of eight symbols of dummy added intothe backend of the 168 symbols of effective data Eff_D is executedduring the time of values of the first eight pieces of data decreasing(see FIG. 5). The four bits of each of the first four symbols are“1111”, “0001”, “0011” and “1111”. This means that in the EDGEtransmission mode, the amplitude value resulting from amplitudemodulation provides a smaller amplitude in comparison to the RMSamplitude value which offers a large constant amplitude. As a result, adigital baseband transmitter signal corresponding to the small amplitudevalue is read out from the internal memory such as a built-in RAM ordata register of the digital RF interface 1 of the RF IC, and suppliedto the digital modulator 2. Hence, the analog baseband transmittersignals TxABI and TxABQ have waveforms of an intermediate-amplitudevalue or a small amplitude value. In this way, it is possible to reduceunwanted radiation important for ramp-down, during which theamplification factors of the RF power amplifiers PA1 and PA2 aredecreased.

<<Reduction in Unwanted Radiation During Ramp-Down>>

FIG. 9 is a plot of assistance in explaining the effect of the reductionin unwanted radiation by the ramp-down operation sequence of thetransmitter according to the embodiment of the invention shown in FIG. 1in the EDGE transmission mode. In GMSK standard, it is defined that inramp-down, the decrease in the RF transmitter signal from each RF poweramplifier varies between the characteristic curves L1 and L2. Thecharacteristic curve L_rp_cnv shows a conventional common ramp-downcharacteristic. Particularly, as to a portion strong in signal intensitydrawn by a broken line, the intensity of the RF transmitter signal canbe changed at a rate over the GMSK standard rate owing to switchingnoise caused at switching circuits in the RF IC, or the manufacturingerror of a semiconductor chip.

The characteristic curve L_rp_inv shows the ramp-down characteristicachieved by the embodiment of the invention shown in FIG. 1. Theintensity of the RF transmitter signal of the portion of theconventional common ramp-down characteristic curve L_rp_cnv drawn by thebroken line is adjusted. As a result, the risk of the intensity of theRF transmitter signal being changed at a rate over the GMSK standardrate owing to switching noise caused at switching circuits in the RF IC,or the manufacturing error of a semiconductor chip is reduced.

<<Switching from GMSK Transmission Mode to Edge Transmission Mode>>

FIG. 10 is a time chart of assistance in explaining an operationsequence in the case of switching GMSK transmission mode (normal burst)to EDGE transmission mode (normal burst).

The first half portion of FIG. 10 shows GMSK transmission mode, in whichonly phase modulation is adopted, and amplitude modulation is notimplemented. Therefore, in the GMSK transmission mode of the first halfportion, in the RF IC of the transmitter according to the embodiment ofthe invention shown in FIG. 1, the amplitude modulation control loop AMLP is not used at all. The back circuit of the phase modulation controlloop PM LP and the back circuit of the amplitude modulation control loopAM LP share the couplers Cp11 and Cp12, the attenuators ATT1 and ATT2,the buffer amplifier BF1, the switch SW1, the down-conversion mixer DCMand the switch SW2. However, in the GMSK transmission mode shown in thefirst half portion of FIG. 10, the feedback to the phase comparator PDin the back circuit of the phase modulation control loop PM LP isparticularly achieved by the passage through the buffer amplifier BF2,the switch SW1, the down-conversion mixer DCM and the switches SW2 andSW3, and the first variable amplifier MVGA is bypassed. Therefore, it isnot necessary to attach importance to unwanted radiation duringramp-down at the time of the end of the GMSK transmission mode of thefirst half portion. Hence, as for the operation sequence shown by FIG.10, no special measure is adopted for ramp-down at the end of the GMSKtransmission mode of the first half portion.

However, in the EDGE transmission mode shown by the latter half portion,not only phase modulation but also amplitude modulation is used.Therefore, in the EDGE transmission mode shown by the latter halfportion, in the RF IC of the transmitter according to the embodiment ofthe invention shown in FIG. 1, the amplitude modulation control loop AMLP is used, too. Hence, in ramp-up in the EDGE transmission mode shownby the latter half portion of FIG. 10, not-straight 1's data of the lastfour symbols of twelve symbols of the effective data Eff_D are used toperform the level down of the transmitter signal in course of ramp-up asin the ramp-up operation sequence in the EDGE transmission mode shown byFIG. 6. Hence, it is possible to reduce unwanted radiation duringramp-up in the EDGE transmission mode shown by the latter half portionof FIG. 10.

<<Switching from Edge Transmission Mode to GMSK Transmission Mode>>

FIG. 11 is a time chart of assistance in explaining an operationsequence in the case of switching the EDGE transmission mode (normalburst) to the GMSK transmission mode (normal burst).

In the EDGE transmission mode shown by the first half portion of FIG.11, not only phase modulation, but also amplitude modulation is used.Therefore, in ramp-down in the EDGE transmission mode shown by the firsthalf portion of FIG. 11, not-straight 1's data of the first four symbolsof eight symbols added into the backend of the effective data Eff_D areused to perform the level down of the transmitter signal in course oframp-down as in the ramp-down operation sequence in the EDGEtransmission mode shown by FIG. 8. Hence, it is possible to reduceunwanted radiation during ramp-down in the EDGE transmission mode shownby the first half portion of FIG. 11. On the other hand, in the GMSKtransmission mode shown by the latter half portion of FIG. 11, onlyphase modulation is adopted, and amplitude modulation is notimplemented. Therefore, it is not necessary to attach importance tounwanted radiation during ramp-up at the time of start of the GMSKtransmission mode shown by the latter half portion of FIG. 11. Hence, asfor the operation sequence shown by FIG. 11, no special measure isadopted for ramp-up at the start of the GMSK transmission mode shown bythe latter half portion.

<<Switching from Access Burst GMSK Transmission Mode to Normal BurstEDGE Transmission Mode>>

FIG. 12 is a time chart of assistance in explaining an operationsequence in the case of switching the GMSK transmission mode of accessburst to the EDGE transmission mode of normal burst.

A communication terminal such as a mobile phone sends a base stationconnection data having a data structure different from that of thenormal burst for sending real transmission data during an operationsequence termed “access burst” in order to notify a base station of itscommunication distance regularly. At the time of sending of accessburst, the operation mode of the RF IC is set to the GMSK transmissionmode. In some cases, after the access burst in the GMSK transmissionmode, an end user can switch the operation mode to the EDGE transmissionmode of normal burst. Switching of transmission mode as shown by FIG. 12is caused in such situation.

Also, in the GMSK transmission mode of access burst of the first halfportion of FIG. 12, only phase modulation is adopted, and amplitudemodulation is not implemented. Therefore, it is not necessary to attachimportance to unwanted radiation during ramp-down at the time of the endof the GMSK transmission mode of access burst of the first half portion.Hence, as for the operation sequence shown by FIG. 12, no specialmeasure is adopted for ramp-down at the end of the GMSK transmissionmode of access burst of the first half portion.

However, in the EDGE transmission mode of normal burst shown by thelatter half portion, not only phase modulation but also amplitudemodulation is used. Therefore, in the EDGE transmission mode shown bythe latter half portion, in the RF IC of the transmitter according tothe embodiment of the invention shown in FIG. 1, the amplitudemodulation control loop AM LP is used, too. Hence, in ramp-up in theEDGE transmission mode of normal burst shown by the latter half portionof FIG. 12, not-straight 1's data of the last four symbols of twelvesymbols of the effective data Eff_D are used to perform the level downof the transmitter signal in course of ramp-up as in the ramp-upoperation sequence in the EDGE transmission mode shown by FIG. 6. Hence,it is possible to reduce unwanted radiation during ramp-up in the EDGEtransmission mode of normal burst shown by the latter half portion ofFIG. 12.

<<RF Transmission Spectra>>

The transmitter according to the embodiment of the invention shown inFIG. 1 enables reduction of unwanted radiation during ramp-up andramp-down in the EDGE transmission mode.

FIGS. 13A and 13B are plots showing RF transmission spectra obtained bya conventional common transmitter which performs ramp-up and ramp-downin the EDGE transmission mode, and RF transmission spectra achieved bythe transmitter according to the embodiment of the invention shown inFIG. 1, respectively. FIG. 13A shows the characteristic of aconventional common transmitter, and FIG. 13B shows the characteristicof the transmitter shown in FIG. 1. The central frequency of RFtransmitter output signals, which are outputs of the RF power amplifiersconnected with the RF IC, is 836.62 MHz within the GSM850 band.

For unwanted radiation at an offset frequency obtained by offset of ±1.8MHz with respect to the central frequency, the GMSK standard requires aquantity of suppression of −36 dBm or larger.

As for the characteristic of the conventional common transmitter shownin FIG. 13A, the margin with respect to the quantity of suppressionaccording to the GMSK standard is insufficient in the vicinity of afrequency of 834.62 MHz near the lower offset frequency. In contrast, ascan be seen from FIG. 13B, in regard to the characteristic of thetransmitter according to the embodiment of the invention as shown inFIG. 1, the margin with respect to the quantity of suppression accordingto the GMSK standard is improved in the vicinity of the frequency of834.62 MHz near the lower offset frequency.

<<Transmitter Supporting Edge Transmission Mode According to PolarModulator System>>

The transmitter supporting the EDGE transmission mode as described aboveadopts the polar loop system, by which the control of ramp-up andramp-down in the EDGE transmission mode is controlled by controlling theamplification factors of the RF power amplifiers PA1 and PA2. However,by use of the polar modulator system, which performs control whilechanging the levels of the RF transmitter input signals supplied toinputs of the RF power amplifiers, it is also possible to controlramp-up and ramp-down in EDGE transmission mode.

FIG. 14 is a diagram showing a transmitter according to anotherembodiment of the invention, which adopts the polar modulator system andsupports the EDGE transmission mode. Specifically, in the RF IC of thetransmitter shown in FIG. 14, the control of ramp-up and ramp-down inthe EDGE transmission mode is conducted by controlling the attenuationfactors and amplification factors of variable amplifiers VGA1 and VGA2connected between inputs of the RF power amplifiers PA1 and PA2 andoutputs of the driver amplifiers DR1 and DR2. Levels of the attenuationfactors and amplification factors of the variable amplifiers VGA1 andVGA2 are controlled by the output of the level converter LVC of the feedcircuit of the amplitude modulation control loop AM LP. Other structuresand operations of the RF IC of the transmitter shown in FIG. 14 aresubstantially the same as those of the RF IC of the transmitter shown inFIG. 1.

<<RF IC Incorporating Receiver>>

The above description has been presented focusing on a transmitter whichperforms EDGE transmission. However, it is needless to say that the RFIC needs the function of a receiver as a matter of course.

<<Multiband Transmission>>

FIG. 15 is a diagram showing the RF IC according to the embodiment ofthe invention more specifically. In a lower portion of the drawing, atransmitter signal-processing circuit is laid out, which is arrangedsubstantially the same as the transmitter signal-processing circuit ofthe RF IC of the transmitter shown in FIG. 1.

GSM850 RF transmitter output signals of 824 to 849 MHz and GSM900 RFtransmitter output signals of 880 to 915 MHz produced in the RF IC aresent out through an output Tx1 of the driver amplifier DR1. Through anoutput Tx2 of the driver amplifier DR2, DCS1800 RF transmitter outputsignals of 1710 to 1785 MHz and PCS1900 RF transmitter output signals of1850 to 1910 MHz produced in the RF IC are sent out. Incidentally, DCSis an abbreviation of Digital Cellular System, and PCS is anabbreviation of Personal Communication System.

<<Frequency Synthesizer>>

In the vicinities of the center of the RF IC shown in FIG. 15 are formedtwo ½ frequency dividers, an RF voltage control oscillator RF VCO, an RFfrequency synthesizer RF Synth, and a system-reference oscillator VCXOfor producing a clock of a system reference frequency of 26 MHz.

<<Receive of Multiband>>

In an upper portion of FIG. 15 is laid out a receive signal-processingcircuit to realize the function of a receiver. The receivesignal-processing circuit includes four low-noise amplifiers LNA1, LNA2,LNA3 and LNA4, two quadrature receive mixers, and a ½ frequency-dividing90-degree phase shifter. To an input Rx1 of the low-noise amplifierLNA1, a GSM850 RF receive input signal of 869 to 894 MHz is supplied. Toan input Rx2 of the low-noise amplifier LNA2, a GSM900 RF receive inputsignal of 925 to 960 MHz is supplied. To an input Rx3 of the low-noiseamplifier LNA3, a DCS1800 RF receive input signal of 1805 to 1880 MHz issupplied. To an input Rx4 of the low-noise amplifier LNA4, a PCS1900 RFreceive input signal of 1930 to 1990 MHz is supplied. The ½frequency-dividing 90-degree phase shifter supplies two mixer circuitsconstituting each quadrature receive mixer with two RF local carriersignals for receiving, which differ in phase by 90 degrees. Hence, thequadrature receive mixers directly convert RF receive input signals intoanalog baseband receive signals RxABI and RxABQ. The analog basebandreceive signals RxABI and RxABQ are passed through the low-pass filtersLPF and then amplified by programmable gain amplifiers PGA. Theresultant baseband amplification signals from the programmable gainamplifiers PGA are supplied to corresponding analog-to-digitalconverters ADC. Then, digital baseband receive signals RxDBI and RxDBQfrom digital filters are supplied to a digital RF interface Dig RF I/F.

<<Digital RF Interface>>

In a right portion of FIG. 15, the digital RF interface Dig RF I/F forinterfacing the RF IC with the baseband LSI to exchange variouscommands, transmission data and various pieces of control data is laidout. The digital RF interface Dig RF I/F adheres to the specificationsof a digital interface described in the Non-patent Document presented byAndrew Fogg, “DigRF BASEBAND/RF DIGITAL INTERFACE SPECIFICATION”.

To the digital RF interface Dig RF I/F is supplied with a control clockCtrlClk, control data CtrlData and a control enable signal CtrlEn. Theirthree lines are used to set operation modes of RF IC idle, transmission,receive, etc.

The digital RF interface Dig RF I/F produces a system clock signalSysClk to be supplied to the baseband LSI from the RF IC.

The digital RF interface Dig RF I/F has terminals for atransmission-and-receive data signal RxTxData andtransmission-and-receive enable signal RxTxEn for bidirectional datacommunication between the RF IC and baseband LSI.

The digital RF interface Dig RF I/F is supplied with a system clockenable signal SysClkEn and a strobe signal Strobe from the baseband LSI.

<<Structure of Mobile Phone>>

FIG. 16 is a block diagram showing a structure of a mobile phoneincorporating the RF IC, the baseband LSI, the power-amplifier modulePAM, the analog front-end module FEM, and the attenuators ATT accordingto the embodiment of the invention as described above.

As in the drawing, an antenna ANT for receive and transmission of themobile phone is connected with a common I/O terminal of the analogfront-end module FEM. The RF IC supplies a control signal FEM_CONT tothe analog front-end module FEM. The flow of RF signals from the antennaANT for receive and transmission to the common I/O terminal of theanalog front-end module FEM is involved in a receive operation RX of themobile phone. The flow of RF signals from the common I/O terminal to theantenna ANT for receive and transmission is involved in a transmissionoperation TX of the mobile phone.

The RF IC converts a transmission baseband signal from the baseband LSIinto an RF transmitter signal to up the frequency, and reverselyconverts an RF receive signal received with the antenna ANT for receiveand transmission into a receive baseband signal to down the frequency,and supplies the resultant signal to the baseband LSI.

An antenna switch in the analog front-end module FEM establishes asignal path between the common I/O terminal and any of transmissionterminals Tx1 and Tx2, and receive terminals Rx1, Rx2, Rx3 and Rx4, andthen the receive operation RX or transmission operation TX is performed.A switch for the transmission and receive operation of an RF signal iscomposed of a HEMT (high electron mobility transistor), and the antennaswitch is composed of a microwave monolithic integrated circuit (MMIC)using a compound semiconductor such as GaAs. The antenna switch MMIC isarranged so that required isolation is achieved by setting the impedanceof a signal path other than the signal path established for the receiveoperation RX or transmission operation TX to an extremely high value. Inthe field of antenna switches, the common I/O terminal is termed “singlepole”, and a total of six terminals consisting of the transmissionterminals Tx1 and Tx2, and the receive terminals Rx1, Rx2, Rx3 and Rx4is termed “6 throw”. Therefore, the antenna switch MMIC (ANT_SW) of FIG.16 is a single pole 6-throw (SP6T: Single Pole 6-throw) type switch.

While the invention made by the inventors has been described above basedon the embodiments specifically, the invention is not so limited. It isneedless to say that various changes or modifications may be madewithout departing from the subject matter hereof.

In the case of the power-amplifier module PAM of the transmitter shownin FIG. 1, couplers operable to detect transmission powers of the RFpower amplifiers electromagnetically or capacitively are adopted as thepower couplers Cp11 and Cp12 for detecting transmission powers of the RFpower amplifiers PA1 and PA2. Alternatively, current sensing typecouplers may be adopted as the power couplers Cp11 and Cp12. In thecurrent sensing type couplers, a small detection DC/AC operating currentproportional to DC/AC operating current of a final-stage power amplifierelement of each RF power amplifier is passed through a detectionamplifier element.

Substantial stop of level up of the RF transmitter signal of the RFpower amplifiers to be supplied to the antenna or level down thereof incourse of ramp-up of the RF transmitter signal can be achieved byadjusting the digital value of the digital ramp data Ramp_Up Data duringramp-up. That is, such stop or level down is enabled by substantiallystopping the increase in the digital value of the digital ramp dataRamp_Up Data or lowering the digital value during ramp-up.

Further, substantial stop of level down of the RF transmitter signal ofthe RF power amplifiers to be supplied to the antenna or level upthereof in course of ramp-down of the RF transmitter signal can beachieved by adjusting the digital value of the digital ramp dataRamp_Down Data during ramp-up. That is, such stop or level up is enabledby substantially stopping the decrease in the digital value of thedigital ramp data Ramp_Down Data or raising the digital value duringramp-down.

In addition, in the above-described embodiments, the RF IC and thebaseband LSI are composed of different semiconductor chips respectively.However, according to another embodiment, the RF IC may be integratedwith the semiconductor chip of the baseband LSI into an integratedone-chip.

What is claimed is:
 1. A transmitter comprising: an RF power amplifierfor producing an RF transmitter signal to be supplied to an antenna; andan RF transmitter signal-processing circuit for converting up a basebandtransmitter signal thereby to produce an RF transmitter input signal tobe supplied to the RF power amplifier, wherein an internal operation ofthe RF transmitter signal-processing circuit is adjusted so that a levelof the RF transmitter signal is raised, then the level of the RFtransmitter signal is substantially stopped from rising, or made todescend, and the level of the RF transmitter signal is raised again in acourse of ramp-up of the RF transmitter signal.
 2. The transmitter ofclaim 1, wherein an internal operation of the RF transmittersignal-processing circuit is adjusted so that the level of the RFtransmitter signal is lowered, then the level of the RF transmittersignal is substantially stopped from going down, or made to ascend, andthe level of the RF transmitter signal is lowered again in a course oframp-down of the RF transmitter signal.
 3. The transmitter of claim 2,wherein ramp-up adjustment data contained in preamble data precedent toreal transmission data transmitted after completion of the ramp-upenables adjustment of the internal operation of the RF transmittersignal-processing circuit in the course of the ramp-up.
 4. Thetransmitter of claim 3, wherein the ramp-up adjustment data and realtransmission data are supplied from a baseband processing unit.
 5. Thetransmitter of claim 3, wherein ramp-down adjustment data contained indummy data added to the real transmission data enables adjustment of theinternal operation of the RF transmitter signal-processing circuit inthe course of the ramp-down.
 6. The transmitter of claim 5, wherein theramp-down adjustment data is supplied from a baseband processing unit.7. The transmitter of claim 5, wherein the RF transmittersignal-processing circuit includes a phase modulation control loop andan amplitude modulation control loop for producing the RF transmitterinput signal by means of phase modulation and amplitude modulation,wherein the amplitude modulation control loop includes therein a firstvariable amplifier having a gain changed according to ramp informationfor the ramp-up and ramp-down, and wherein the ramp-up and ramp-down areenabled by controlling the gain of the first variable amplifieraccording to the ramp information.
 8. The transmitter of claim 7,wherein the amplitude modulation control loop includes therein a secondvariable amplifier having a gain changed opposite in direction to thechange in the gain of the first variable amplifier in response to theramp information.
 9. The transmitter of claim 8, wherein the amplitudemodulation control loop constitutes one of a polar loop and a polarmodulator for EDGE transmission.
 10. An RF transmitter signal-processingcircuit arranged so as to be connected with an RF power amplifier forproducing an RF transmitter signal to be supplied to an antenna of atransmitter, the RF transmitter signal-processing circuit converting upa baseband transmitter signal thereby to produce an RF transmitter inputsignal to be supplied to the RF power amplifier, wherein an internaloperation of the RF transmitter signal-processing circuit is adjusted sothat a level of the RF transmitter signal is raised, then the level ofthe RF transmitter signal is substantially stopped from rising, or madeto descend, and the level of the RF transmitter signal is raised againin a course of ramp-up of the RF transmitter signal.
 11. The RFtransmitter signal-processing circuit of claim 10, wherein an internaloperation of the RF transmitter signal-processing circuit is adjusted sothat the level of the RF transmitter signal is lowered, then the levelof the RF transmitter signal is substantially stopped from going down,or made to ascend, and the level of the RF transmitter signal is loweredagain in a course of ramp-down of the RF transmitter signal.
 12. The RFtransmitter signal-processing circuit of claim 11, wherein ramp-upadjustment data contained in preamble data precedent to realtransmission data transmitted after completion of the ramp-up enablesadjustment of the internal operation of the RF transmittersignal-processing circuit in the course of the ramp-up.
 13. The RFtransmitter signal-processing circuit of claim 12, wherein the ramp-upadjustment data and real transmission data are supplied from a basebandprocessing unit.
 14. The RF transmitter signal-processing circuit ofclaim 12, wherein ramp-down adjustment data contained in dummy dataadded to the real transmission data enables adjustment of the internaloperation of the RF transmitter signal-processing circuit in the courseof the ramp-down.
 15. The RF transmitter signal-processing circuit ofclaim 14, wherein the ramp-down adjustment data is supplied from abaseband processing unit.
 16. The RF transmitter signal-processingcircuit of claim 14, wherein the RF transmitter signal-processingcircuit includes a phase modulation control loop and an amplitudemodulation control loop for producing the RF transmitter input signal bymeans of phase modulation and amplitude modulation, wherein theamplitude modulation control loop includes therein a first variableamplifier having a gain changed according to ramp information for theramp-up and ramp-down, and wherein the ramp-up and ramp-down are enabledby controlling the gain of the first variable amplifier according to theramp information.
 17. The RF transmitter signal-processing circuit ofclaim 16, wherein the amplitude modulation control loop includes thereina second variable amplifier having a gain changed opposite in directionto the change in the gain of the first variable amplifier in response tothe ramp information.
 18. The RF transmitter signal-processing circuitof claim 17, wherein the amplitude modulation control loop constitutesone of a polar loop and a polar modulator for EDGE transmission.
 19. Amethod for operating the transmitter comprising: a preparation step ofpreparing an RF power amplifier for producing an RF transmitter signalto be supplied to an antenna, and an RF transmitter signal-processingcircuit for converting up a baseband transmitter signal thereby toproduce an RF transmitter input signal to be supplied to the RF poweramplifier; a ramp-up adjustment step of adjusting an internal operationof the RF transmitter signal-processing circuit so that a level of theRF transmitter signal is raised, then the level of the RF transmittersignal is substantially stopped from rising, or made to descend, and thelevel of the RF transmitter signal is raised again in a course oframp-up of the RF transmitter signal; and a ramp-up step of making theRF transmitter signal ramp up after the ramp-up adjustment step.
 20. Themethod for operating the transmitter of claim 19, further comprising: aramp-down adjustment step of adjusting an internal operation of the RFtransmitter signal-processing circuit so that the level of the RFtransmitter signal is lowered, then the level of the RF transmittersignal is substantially stopped from going down, or made to ascend, andthe level of the RF transmitter signal is lowered again in a course oframp-down of the RF transmitter signal; and a ramp-down step of makingthe RF transmitter signal ramp down after the ramp-down adjustment step.21. The method for operating the transmitter of claim 20, wherein theramp-up adjustment step, ramp-up step, ramp-down adjustment step andramp-down step are controlled by software programs stored in anon-volatile storage device incorporated in the transmitter.
 22. Atransmitter comprising: an RF power amplifier for producing an RFtransmitter signal to be supplied to an antenna; and an RF transmittersignal-processing circuit for converting up a baseband transmittersignal thereby to produce an RF transmitter input signal to be suppliedto the RF power amplifier, wherein an internal operation of the RFtransmitter signal-processing circuit is adjusted so that a level of theRF transmitter signal is lowered, then the level of the RF transmittersignal is substantially stopped from going down, or made to ascend, andthe level of the RF transmitter signal is lowered again in a course oframp-down of the RF transmitter signal.
 23. The transmitter of claim 22,wherein ramp-down adjustment data contained in dummy data added to areal transmission data enables adjustment of the internal operation ofthe RF transmitter signal-processing circuit in the course of theramp-down.
 24. The transmitter of claim 23, wherein the ramp-downadjustment data is supplied from a baseband processing unit.
 25. Atransmitter comprising: an RF power amplifier for producing an RFtransmitter signal to be supplied to an antenna; and an RF transmittersignal-processing circuit for converting up a baseband transmittersignal thereby to produce an RF transmitter input signal to be suppliedto the RF power amplifier, wherein a ramp-up of the RF transmittersignal is controlled by ramp information supplied form a basebandprocessing unit, and wherein an internal operation of the RF transmittersignal-processing circuit is adjusted so that a level of the RFtransmitter signal is raised, then the level of the RF transmittersignal is substantially stopped from rising, or made to descend, and thelevel of the RF transmitter signal is raised again in a course of theramp-up of the RF transmitter signal.
 26. The transmitter of claim 25,wherein a ramp-down of the RF transmitter signal is controlled by theramp information supplied from a baseband processing unit, and whereinan internal operation of the RF transmitter signal-processing circuit isadjusted so that the level of the RF transmitter signal is lowered, thenthe level of the RF transmitter signal is substantially stopped fromgoing down, or made to ascend, and the level of the RF transmittersignal is lowered again in the course of the ramp-down of the RFtransmitter signal.
 27. The transmitter of claim 26, wherein the RFtransmitter signal-processing circuit includes a phase modulationcontrol loop and an amplitude modulation control loop for producing theRF transmitter input signal by means of phase modulation and amplitudemodulation, the amplitude modulation control loop includes therein afirst variable amplifier having a gain changed according to the rampinformation for the ramp-up and the ramp-down, and the ramp-up and theramp-down are enabled by controlling the gain of the first variableamplifier according to the ramp information.
 28. The transmitter ofclaim 27, wherein the amplitude modulation control loop includes thereina second variable amplifier having a gain changed opposite in directionto the change in the gain of the first variable amplifier in response tothe ramp information.
 29. The transmitter of claim 28, wherein theamplitude modulation control loop constitutes one of a polar loop and apolar modulator for EDGE transmission.